Hello: I am trying to make a 1923 Bungalow in the Seattle area livable. I’m currently working on the basement and am a disciple of Lugano and Lstiburek. I’m wondering if you HVAC experts could answer a few questions:
1. I have a section that is crawlspace. I am sealing it up and insulating the walls. I will not insulate the crawl space ceiling (I want to treat the crawl space as living area). What would be a R or U value for the crawlspace floor (plastic over dirt)? Is it cost effective to put down some 2″ foam over the plastic?
2. Basement floor: What would be a R or U value for a concrete basement floor? How bad is this uninsulated basement floor hurting me? Is most of the heat loss at the edge of the slab (thru the concrete walls)?
Thank you very much!
Dave LaBarge
Replies
1. R approx 1 only.
2. "living space" and "basement floor/edge of slab" descriptions do not compute. The 'Rvalue' of your basement floor depends on if there is a layer of dry gravel under it or not. Also VERY dependent on the amount of ground water moverment. If you have moving ground water under the floor, R <1. If 'bone dry' soil, R value (after all the soil is heated up over a few weeks) can be large, as in > 20. Very unlikely your soil is dry in Seattle area. Temp differental to ground is to 53F or so. When temp is in the 30's, without ground water movement under the floor, most or your heat is out the walls. If the 'crawl space' has relatively 'dead' air (little air movement other than normal convection), there will likely be a relatively low temp differential across the floor.
At own house in PNW I have the upper 5 feet of the basement walls insulated, 4" of gravel under the floor with drains to avoid ground water effects.
Junkhound: Thanks for the response! If the dirt+Plastic on my crawlspace floor is only R1, I need to do something about that. Would you recommend some 2" foam over the plastic with taped joints? By "living space" I just meant "conditioned" as opposed to vented to outside air. Regarding the edge of slab comment: I thought I remembered from my HVAC class in college that most of the heat loss thru a concrete slab was via the edge. I see from your explanation that is not correct.
Dave